Drain device and method

ABSTRACT

The present invention provides a drain device for a transporting box with an input/output opening which can be blocked by a box door and which contains substrate wafers stacked according to parallel planes. The drain device comprises a volume limited by a sealed wall divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with the two parts being separated by a sealed partition, and a range of guides defining the openings arranged parallel to those of the wafers and connecting with the volume of the drain device to direct the purging gas towards the transporting box.

REFERENCE

This application is based on and claims the benefit of French patent application Ser. No. 08/54,769, filed on Jul. 11, 2008, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a drain device for a transporting box used for the displacement of semiconductor substrates between the different stages in the production of semiconductor and microelectronic components, for example for the production of micro-electro-mechanical system (MEMS) or micro-opto-electro-mechanical system (MOEMS) components.

BACKGROUND

During production, the substrates, such as masks or slices of silicon 200 mm or 300 mm in diameter for example, are transported in transporting boxes which protect them against the pollution present in the atmosphere in clean rooms.

The transporting boxes have the advantage of being able to maintain a controlled atmosphere around the substrates, in which the presence of contaminating products is avoided as far as possible. For the transport of substrates in wafers 300 mm in diameter, one particular type of transporting box is used, known as an FOUP (“Front Opening Unified Pod”), comprising a sealed peripheral wall with a lateral input-output opening, which can be blocked by a door equipped with sealing means. In a transporting box, the wafers are stacked on top of each other in a sort of rack, which may also be referred to as a cassette or a basket. The basket containing up to 25 wafers is generally placed or held on the wall which constitutes the base of the transporting box.

The transporting box may be coupled to an input-output interface for the semiconductor component manufacturing equipment. The interface is a system allowing the transporting box to be positioned and its door to be opened. The interface usually comprises robotic means of activating the door to open and close the door of the transporting box. This interface (sometimes also known as a mini-environment), is usually known as an Equipment Front End Module, or EFEM.

Control of the contamination during the production of electronic chips is a major challenge for the semiconductor industry. The contamination may be caused by particles or gases, which cause corrosion or form crystals on the wafers for example. Contamination may have dramatic consequences for chip manufacturers since the performances of the chip will be severely reduced by these faults.

There are solutions to limit the contamination by installing drain systems in the substrate transporting boxes, advantageously using the vacuum or a neutral gas. However, these drain systems may only be used when the transporting box is detached from the equipment (US-2007-062,561; JP-2007-317 909), in other words when it is closed. This causes two problems.

The first problem concerns the duration of the draining operation, in other words the time to replace the contaminated atmosphere inside the transporting box with a clean neutral gas, for example nitrogen. Therefore, draining a closed transporting box requires the clean gas to be injected through drain ports which have the disadvantage of not being standard and which have a limited effect. It therefore takes more than 10 minutes to incompletely drain a box (R. Bernard and A. Favre: “Using numerical simulation to optimize 300 mm FOUP purging”, Solid State Techn., October 2003, p. 71). Furthermore, the vacuum process requires the transporting box to be placed in a vacuum and a return to atmospheric pressure progressively so as avoid the risk of damaging the box.

The second problem is that a transporting box containing the substrates may remain connected to the equipment for several hours. Even though it is possible to carry out a draining operation after having treated the entire batch of substrates contained in the transporting box, irreversible faults have already appeared.

SUMMARY

The invention in one implementation encompasses a drain device for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked based on parallel planes. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts. The drain device also comprises a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box.

The invention in another implementation encompasses a drain system of a transporting box, with an input/output opening which a box door can block and containing a stack of substrate wafers based on parallel planes, using a drain device for the transporting box. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box. The drain system comprises a chamber with at least one connection orifice to a transporting box equipped with a chamber door, and comprising means of activating the box door to open and close the door of the transporting box and means of activating the drain device to connect it to the transporting box.

In yet another implementation, the invention encompasses a drain method for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked according to parallel planes, using a drain device for the transporting box. The drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box. The drain device is connected to the input/output opening of the transporting box. A purging gas is injected in the upper part of the volume of the drain device through the purging gas inlet orifice. The gas is inserted into the transporting box through openings, the median plane of which is parallel to the wafer planes and which connect with the upper part of the volume of the drain device. The gas is collected through openings, the median plane of which is parallel to the wafer planes and which connect with the lower part of the volume of the drain device. The gas is evacuated through the purging gas outlet orifice in the lower part of the volume of the drain device.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention will become apparent upon reading the following description of one embodiment, which is naturally given by way of a non-limiting example, and in the attached drawing, in which:

FIG. 1 shows in diagram form a substrate treatment installation to which a transporting box is connected,

FIGS. 2 a, 2 b and 2 c show in diagram form the way in which a FOUP transporting box is connected to a drain system according to one embodiment of the invention,

FIGS. 3 a and 3 b represent perspective views, of the two faces respectively, of a drain device according to one embodiment of the invention,

FIG. 4 shows a perspective view of one of the faces of a drain device according to another embodiment of the invention,

FIG. 5 shows the path of the purging gas between the different planes in a transporting box coupled to the purging device of FIGS. 3 a and 3 b.

DESCRIPTION OF EMBODIMENTS

One embodiment of the present invention provides a device to effectively drain an FOUP transporting box, containing substrate wafers, while it is still connected to the equipment.

The invention also provides a drain device which can be adapted to all standard FOUP type transporting boxes.

A wafer is extracted or inserted into the transporting box approximately every 2 to 3 minutes. It is therefore a time constraint to carry out the draining operation as a background task during the treatment of a batch of substrates. The invention therefore also provides a draining method which can be used to obtain an efficient draining of a FOUP transporting box in under 3 minutes when it is connected to the equipment.

The present invention provides a drain device for a transporting box with an input/output opening which can be blocked by a box door and which contains substrate wafers stacked on parallel planes, comprising:

-   -   a volume, limited by a wall, divided into at least an upper part         equipped with a purging gas inlet orifice and a lower part         equipped with a purging gas outlet orifice, with the two parts         being separated by a sealed partition, and     -   a main wall, intended to cooperate with the input/output opening         of the transporting box, roughly perpendicular to the planes of         the wafers and comprising a range of openings, the median plane         of which is parallel to the planes of the wafers, with the         openings connecting the volume of the drain device to the         transporting box.

According to one preferential execution method, the dimensions of the openings in relation to the purging gas inlet orifice are such that the upper part of the drain device is in overpressure. It is understood that the total surface area of the connection openings between the upper part of the drain device and the transporting box must be sufficiently small.

The number of openings should preferably be at least equal to the number of wafers contained in the transporting box so as to direct the purging gas respectively towards each wafer. Transporting boxes may usually contain between 1 and 25 wafers.

According to a first embodiment of the invention, the openings are rectangular slots. Advantageously, the openings have a length of the same order of magnitude as the diameter of the substrate wafers. Preferably, the rectangular slots have a height of less than the distance separating two successive wafers, or around 10 mm, and the slots are preferably less than 3 mm high.

According to a second embodiment, the openings consist of aligned holes. Advantageously, the holes are aligned over a distance of the same order of magnitude as the diameter of the substrate wafers. The holes are preferably circular and have a diameter lower than the distance separating two successive wafers, and the holes preferably have a diameter of less than 2 mm.

According to one variant, the drain device comprises among other things a range of guides inserted between the openings. The number of guides is preferably at least equal to the number of wafers contained in the transporting box. These guides are used to direct the gas stream as close as possible to the wafers.

According to one execution method, the guides have a length of the same order of magnitude as the diameter of the substrate wafers.

According to another execution method of the invention, the guides are arranged in the planes of the wafers. Therefore, each guide is presented in the same plane as the wafer to which it corresponds. Advantageously, the end of each guide has a concave form which matches the form of the corresponding circular wafer.

Preferably, the drain device also comprises sealed connection means at the input/output opening of the transporting box.

The invention also provides a system for draining, using the drain device described previously, a transporting box with an input/output opening which can be blocked by a box door and containing a stack of substrate wafers. According to one embodiment of the invention, the drain system comprises a chamber, with at least one connection orifice to a transporting box equipped with a chamber door, and comprises means of activating the box door to open and close the transporting box door and means of activating the drain device to connect it to the transporting box.

The idea is to affix a drain device forming a door in the place of the door of the transporting box, and to use this drain device to inject a clean gas into the transporting box.

The drain system also comprises sealing means at the coupling zone of the connection orifice to the input/output opening of the transporting box.

The invention also provides a method for draining, using the drain device described previously, a transporting box with an input/output opening which can be blocked by a box door and containing substrate wafers stacked on parallel planes. According to one embodiment of the invention, the method includes the following stages:

-   -   the drain device is connected to the input/output opening of the         transporting box,     -   a clean gas is injected into the upper part of the volume of the         drain device through the purging gas inlet orifice,     -   the gas is inserted into the transporting box through openings,         the median plane of which is parallel to the wafer planes and         which connects with the upper part of the volume of the drain         device,     -   the gas is collected through openings, the median plane of which         is parallel to the wafer planes and which connects with the         lower part of the volume of the drain device,     -   the gas is evacuated through the purging gas outlet orifice in         the lower part of the volume of the drain device.

Advantageously, the purging gas is injected into the upper part of the drain device at a pressure greater than 2 bars.

The drain method with the drain device according to one embodiment of the invention acts by forced convection between the substrate wafers. It is used to gain efficiency in relation to existing drain devices acting by diffusion. The draining operation is quicker: 1 minute instead of several minutes. After 1 minute of circulation of the purging gas at 50 slm, there remains on average less than 3.4% dioxygen in the transporting box.

This drain device and this drain method can be used with all FOUP type transporting boxes currently in service.

For an equivalent flow, the neutral gas enters the transporting box at a much lower speed than if the draining is carried out using drain orifices arranged in the back wall of the standard transporting boxes. For this reason, there are fewer particles detached and blown inside the transporting box. Furthermore, backscattering is not possible for these particles, therefore the wafers are protected against any risk of redeposition.

The draining operation may be used either at the end of the treatment before reclosing and disconnecting the transporting box, or as a background task during the treatment between two wafer transfer operations. The time required to reach a draining efficiency of greater than 90% is less than 2 minutes with a purging gas flow of 30 slm. This time is shorter than the duration passing between two wafer transfers.

A substrate treatment installation is shown in FIG. 1. It contains a process chamber 1, maintained in a vacuum in which manufacturing or treatment operations are carried out for substrates such as semiconductor wafers. The process chamber 1 connects to a transfer chamber 2, also in a vacuum, in which the wafer is placed immediately before and after its treatment in the process chamber 1. The transfer chamber 2 connects to a loading/unloading lock 3 in which the vacuum and return to atmospheric pressure phases alternate. This lock 3 connects the transfer chamber 2 to an EFEM module 4 used to transfer substrates at atmospheric pressure. One or more removable transporting boxes 5, of the FOUP type for example, may be connected via an orifice 6 to the EFEM module 4. These boxes 5 are used for the storage or the transport of substrates at atmospheric pressure, in particular between two manufacturing phases or between two treatment devices. The substrate wafers stacked in a basket 7 may therefore be transferred one by one to the transfer chamber 2 via the EFEM module 4 and the lock 3.

FIGS. 2 a, 2 b and 2 c correspond to the successive stages of the coupling of a FOUP type transporting box to the drain device according to one embodiment of the invention.

FIG. 2 a shows a drain system 20 according to one embodiment of the invention comprising a chamber 21 with sealed walls comprising at least one orifice 22 to allow the coupling of a transporting box 23. A basket 24 containing substrate wafers arranged horizontally is placed in the transporting box 23. The transporting box 23 comprises side walls 23 a, a top wall 23 b and a bottom wall 23 c on which the basket rests 24. In one of the side walls 23 a, there is an input/output opening blocked by a door 25. The door 25 is placed opposite the orifice 22 of the drain system 20. A drain device 26 according to one embodiment of the invention is placed in the lower part of the chamber 21. If the drain system 20 provides the functions of an EFEM module, it also comprises a second orifice 27 able to be connected to the loading/unloading lock for a substrate treatment installation.

Once the transporting box 23 is placed opposite the orifice 22 of the drain system 20, its door 25 is unlocked using means of activating the box door, then moved to the lower part of the chamber 21 for example, in order not to hinder the displacement of the wafers to the loading/unloading lock, as shown in FIG. 2 b.

The drain device 26 is positioned by robotic means of activation in the place of the door 25 of the transporting box 23 in order to drain the transporting box 23 and the substrate wafers it contains, as shown in FIG. 2 c. The drain device 26 is applied to the box 23 to seal it closed. This operation to put in place the drain device 26 may be carried out at the end of the treatment of the entire batch of substrates and/or between each displacement of wafers to the method chamber.

A specific embodiment of the drain device according to the invention is represented in FIGS. 3 a and 3 b. The drain device 30 comprises a volume limited by a sealed wall divided into an upper part 31 and a lower part 32 by a sealed separating partition 33. The upper part 31 comprises an inlet orifice 34 for the purging gas. The lower part 32 comprises an outlet orifice 35 for the evacuation of the gas. The volume of the drain device is closed on the drain system chamber side by a sealed wall (not shown) and open towards the inside of the transporting box. The drain device 30 comprises horizontal guides 36 which restrict the openings 37, the number of which must be equal to the number of wafers contained in the basket. The input/output opening of the box has dimensions slightly greater than the diameter of the substrate wafers in order to allow passing. The drain device 30 which blocks it as a replacement for the box door shall therefore have similar dimensions, and the guides 36 and the openings 37 shall therefore have a length of the same order of magnitude as that of the wafers. In the present case, the openings 37 are rectangular slots with a length of around 300 mm and a height of less than 3 mm. The end of each guide 36 is concave 38, matching the form of the circular wafer arranged horizontally in the basket, in order to bring the purging gas as close as possible to each wafer to sweep over the surface. A joint 39 ensures the sealing of the connection between the transporting box and the drain device 30.

FIG. 4 shows a perspective of another embodiment of a drain device 40 comprising a gas inlet orifice 41. Here, the openings 42 consist of parallel rows of holes 43, each horizontal row corresponding to the horizontal plane of a wafer. The drain device 40 does not contain guides.

The drain method will now be described in reference to FIG. 5. A drain device 50 according to one embodiment of the invention is connected and sealed to the input/output opening of a transporting box 51 so as to connect the volume of the drain device 50 to the inside of the transporting box 51. A clean purging gas, preferably a neutral gas, is injected through the gas inlet orifice 52 in the upper part 53 of the drain device volume 50, advantageously at a pressure greater than 2 bars. The purging gas is then directed through the openings 54 by the guides 55 around and towards the inside of the basket 56. The purging gas flow travels in parallel to the planes of the wafers 57, to the planes of the guides 55 and to the median planes of the openings 54, as shown by arrows 58 and 59 respectively.

After flushing the wafers located in the top of the basket 56, the purging gas returns to the lower part 60 of the drain device volume 50, flushing the wafers located in the bottom of the basket 56, as shown by arrows 61 and 62. The purging gas then escapes through the outlet orifice 63.

The openings 54 are dimensioned in relation to the gas inlet orifice 52 in such a way that the upper part 53 of the drain device 50 is in slight overpressure, in order that the neutral and clean gas can enter homogeneously in the transporting box 51. The openings 54 may take the form of slots with a low height or a series of aligned holes with a low diameter, for example with a diameter of less than 2 mm. A low cross section for these openings 54 allows gas input with homogeneous distribution over the entire surface of the upper part 53 of the drain device 50. 

1. Drain device for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked based on parallel planes, comprising: a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the inpuVoutput opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box.
 2. Drain device according to claim 1, in which the dimensions of the openings in relation to the purging gas inlet orifice are such that the upper part of the drain device is in overpressure.
 3. Drain device according to claim 2, in which the number of openings is at least equal to the number of wafers contained in the transporting box.
 4. Drain device according to claim 2, in which the openings are rectangular slots with a length of the same order of magnitude as the diameter of the substrate wafers.
 5. Drain device according to claim 2, in which the openings consist of holes aligned over a distance of the same order of magnitude as the diameter of the substrate wafers.
 6. Drain device according to claim 1, in which the number of openings is at least equal to the number of wafers contained in the transporting box.
 7. Drain device according to claim 1, in which the openings are rectangular slots with a length of the same order of magnitude as the diameter of the substrate wafers.
 8. Drain device according to claim 1, in which the openings consist of holes aligned over a distance of the same order of magnitude as the diameter of the substrate wafers.
 9. Drain device according to claim 1, also comprising a range of guides inserted between the openings.
 10. Drain device according to claim 9, in which the number of guides is at least equal to the number of wafers contained in the transporting box and the guides are arranged in the planes of the wafers.
 11. Drain device according to claim 10, in which each guide is arranged in the same plane as the wafer to which it corresponds, with the end of each guide being concave, matching the form of the corresponding circular wafer.
 12. Drain device according to claim 1, also comprising means for a sealed connection to the input/output opening of the transporting box.
 13. Drain system of a transporting box, with an input/output opening which a box door can block and containing a stack of substrate wafers based on parallel planes, using a drain device for the transporting box; wherein the drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box; wherein the drain system comprises a chamber with at least one connection orifice to a transporting box equipped with a chamber door, and comprising means of activating the box door to open and close the door of the transporting box and means of activating the drain device to connect it to the transporting box.
 14. Drain method for a transporting box with an input/output opening which a box door can block and which contains substrate wafers stacked according to parallel planes, using a drain device for the transporting box; wherein the drain device comprises a volume, limited by a sealed wall, divided into at least an upper part with a purging gas inlet orifice and a lower part with a purging gas outlet orifice, with a sealed partition separating the two parts, and a main wall, intended to cooperate with the input/output opening of the transporting box, roughly perpendicular to the planes of the wafers and comprising a range of openings, the median plane of which is parallel to the planes of the wafers, with the openings connecting the volume of the drain device to the transporting box; the drain method comprising: connecting the drain device to the input/output opening of the transporting box, injecting a purging gas in the upper part of the volume of the drain device through the purging gas inlet orifice, inserting the gas into the transporting box through openings, the median plane of which is parallel to the wafer planes and which connect with the upper part of the volume of the drain device, collecting the gas through openings, the median plane of which is parallel to the wafer planes and which connect with the lower part of the volume of the drain device, evacuating the gas through the purging gas outlet orifice in the lower part of the volume of the drain device.
 15. Drain method according to claim 14, including the injection of purging gas into the upper part of the drain device at a pressure greater than 2 bars. 